Recording apparatus and method employing photoelectroviscous ink

ABSTRACT

A METHOD AND APPARATUS FOR IMAGE RECORDING BY THE USE OF A PHOTOELECTROVISCOUS FLUID FORMED OF A SHEET DIELECTRIC LIQUID CONTAINING ORGANIC PHOTOCONDUCTIVE PIGMENTS IS DISCLOSED. THE FLUID IS MAINTAINED UNDER PRE

7 L.M.CARREIRA ETAL 3,553,708

APPARATUS AND METHOD EMPLOYING PHOTOELECTROVISCOUS INK Original FiledJan. 26. 1966 2 Sheets-Sheet 1 SIGNAL SOURCE' FIG. 1

23 CONTROLLED PRESSURE ATTORNEYS Jan. 5,1971 LMCARRQRA HAL 3,553,708

APPARATUS AND METHOD EMPLOYING PHOTOELECTROVI SCOUS INK Original FiledJan. 26. 1966 2;Sheets-Sheet a 3" 6 EZ- I /4 l8 9 b L CONTROLLED 22PRESSURE CONTROLLED PRESSURE INVENTORS LEONARD M. CARREIRA VSEVOLOD S.MIHAJLOV M flbmm A T TORNEVS United States Patent 01 fice 3,553,708Patented Jan. 5, 1971 3,553,708 RECORDING APPARATUS AND METHOD EM-PLOYING PHOTOELECTROVISCOUS INK Leonard M. 'Carreira, Webster, andVsevolod S. Mihajlov, Rochester, N.Y., assignors to Xerox Corporation,Rochester, N.Y., a corporation of New York Continuation of applicationSer. No. 523,189, Jan. 26, 1966. This application Feb. 21, 1968, Ser.No. 707,331 Int. Cl. G01d 5/26, 5/16 US. Cl. 346-1 Claims ABSTRACT OFTHE DISCLOSURE A method and apparatus for image recording by the use ofa photoelectroviscous fluid formed of a select dielectric liquidcontaining organic photoconductive pigments is disclosed. The fluid ismaintained under pressure at an electrode aperture to which a constantfield is applied and the flow of the fluid through the aperture onto arecording surface is controlled in response to a light signal appliedthereto.

This is a continuation of application Ser. No. 523,189, filed Jan. 26,1966, and now abandoned.

This invention relates to a system for image recording and moreparticularly to method and apparatus for imaging with aphotoelectroviscous fluid in response to light modulated signals.

It has been shown by Willis M. Winslow that the apparent viscosity ofcertain liquids can be markedly altered by applying an electric voltageor electric field to these materials. (Journal of Applied Physics 20,P137 (1949), U.'S. Pats. 2,417,850; 2,661,596; 2,661,825; 2,663,809;3,047,507.) Generally speaking, these liquids comprise a suspension ofmicron sized solid particles in a liquid carrier. It is desirable tohave a certain amount of water present as an adsorbed layer on theparticles, and various other materials are known to be desirableadditives.

The effect of an electric voltage on these liquids may be termed theelectroviscous or lectroviscosity effect and the liquids themselves aretermed electroviscous liquids. The phenomenon is generally defined asthe increase in torque necessary to maintain a given rate of shear ofvarious liquids or suspensions under the influence of an electric field.This increase in torque is usually measured by a device called aBrookfield viscometer which includes a rotating flat disc (spindle) in afluid at a constant angular velocity and measures the torque necessaryto overcome the viscous resistance of the fluid. As shown, for example,by Winslow the viscosity of electroviscous liquids can be varied inaccordance with the particular ingredients and proportions employed aswell as by voltage. A viscosity of about 1000 poises, in the absence ofany voltage, has been found to be particularly desirable. When a voltageis applied to the electroviscous fluid, it has been found that theliquid does not actually undergo a change in viscosity in the strictsense, but

instead, the liquid jells or becomes grease-like. This indicates thatthe liquid, when a voltage is applied, will not flow at all unless acertain minimum force is applied which force is actually related to theapplied voltage. This aspect of the electroviscous effect was notpreviously known but is very beneficial for the present invention inwhich the flow is controlled by the use of fluids having photoconductivesensitivity. The Winslow patents and publications noted above includenumerous formulas for electroviscous liquids certain of which whenmodified as hereinafter described may be used in connection with thepresent invention.

The use of electroviscous fluids for image recording is disclosed incopending application, Ser. No. 313,675 filed Oct. 3, 1963 in the nameof Clark, now Pat. No. 3,270,637, and is incorporated herein byreference. The present invention is likewise concerned with imagerecording, and therefore it is desirable that the liquids employed havea dark or readily visible color effected by the use of dyes or othersuitable coloring matter. Other types of homogeneous liquids alsoexhibit an electroviscous effect and when appropriately modified areuseful in the present invention. These include where suitable; solutionsof metal soaps in non-polar hydrocarbons; mixtures of mutually solublesubstances which can exist as solid or liquid solutions at differenttemperatures and which may exist in the liquid crystalline state inliquid solutions; solutions of paraflin sulfates which form miceles; andliquid crystals, i.e. elongated molecules which contain one or morepolar groups and which form nematic, smectic, or cholesteric phases.Further information on non-particulate electroviscous materials may befound in the literature, e.g. Bjornstahl and Snellman, KolloidZeitschrift, vol. 78, p. 258; Bjornstahl and Snellman, KolloidZeitschrift, vol. 86, p. 223 (1939); Michailoff and Zwetkoff, ActsPhysicochimica U.R.S.S., vol. 10, p. 415 (1939).

Now in accordance with the instant invention there has been discoveredthat certain insulating oils or other dielectric liquids disclosed aboveand a will be further described, when containing quantities ofphotosensitive materials will display a change in electroviscous effectin response to actinic radiation. By applying radiation as signalsrepresenting intelligence information to the fluid under pressure and inthe presence of an applied field, the flow thereof can becorrespondingly controlled to effect image recording onto a recordingmedia as in a facsimile system.

It is therefore an object of this invention to provide a novel recordingsystem for image recording of information intelligence.

It is a further object to provide novel method and apparatus for imagerecording by means of electroviscous liquids selectively flow responsiveto applied signals of information intelligence in the form of actinicradiation.

It is a still further object of the invention to provide novelcompositions of electroviscous liquids having photoconductive propertiesas to display a change in electroviscous eifect in response to appliedactinic radiation.

Further objects and features of the invention will become apparent uponreading the following description in conjunction with the drawingswherein:

FIG. 1 is a sectional elevation of a simplified apparatus emobdiment inaccordance with the invention;

FIG. 2 is a schematic isometric View of an apparatus embodiment inaccordance herewith to effect a facsimile reproduction from an originaldocument;

FIG. 3 is an enlarged side elevation of the document scanning mechanismemployed in FIG. 2;

FIG. 4 is a schematic apparatus variation of FIG. 2 for effecting areversed optical signal;

FIG. 5 is a schematic isometric view of an apparatus embodiment forreproducing from a source of intelligence voltage signals; and

FIG. 6 is a schematic isometric of alternate apparatus for directscanning of an image document.

Essential to the invention hereof is the fluid or ink composition whichas light sensitivity to the extent that the composition by virtue of itsfluid properties or the properties of contained particles changes itsviscosity when a field is applied in the presence of light. Thus, aswill be understood from the description below, the ink composition inthe preferred arrangement is contained under pressure between electrodesto which an electrical field is applied. The pressure is sufiicient toeffect flow in the absence of a light signal. That is, in the absence ofa light signal the composition has sufficiently low viscosity to flowpast the electrodes onto a closely spaced recipient surface. Applicationto the ink fluid of a light signal, representative of intelligence to berecorded, irrespective of its origin whether it be a transduced computeroutput, the images from the surface of a scanned documet, or the like,causes the fluid viscosity to be changed sufiicient to arrest flow. Thischanged viscosity, effected intermittently in correlation to informationbeing recorded, enables controlled flow onto a closely spaced recordingmember on which a reproduction is formed. The period of flowinterruption corresponds accurately to the duration of the appliedradiation such that fiow is resumed or restored when the radiationsignal is removed. Accordingly, the ink composition as above statedshould'preferably be colored, or contain a color former or otherwise becapable of marking a receiving sheet. It should likewise containquantities of photosensitive materials whereby its viscosity can beselectively controlled in response to an applied signal of actinicradiation. The viscosity varying agent may comprise any suitablephotosensitive material. Typical photosensitive materials includeMonastral Green B, 0.1. No. 74260, a phthalocyanine pigment availablefrom E. I. du Pont de Nemours & Co.; Indofast Yellow Toner, C.I. No.70600, fiavanthrone, available from Harmon Color; Quindo Magenta RV-6803, a substituted quinacridone, available from Harmon Color; AlgolYellow GC, C.I. No. 67300, 1,2,5,6-di-(C,C-diphenyl)thiazole-anthraquinone, available from General Dye Stufls;Indofast Brilliant Scarlet Toner, C.I. No. 71140, 3,4,9,10-bis(n,N'-(p-methoxyphenyl)-imido)- perylene, available from Harmon Color;Skyline Blue B-4712, CI. 74160, copper phthalocyanine available fromHarmon Color; Monolite Fast Blue GS, a mixture of alpha and betaphthalocyanine, available from Arnold Hoffman Co.; Phosphor 2225, amixed cadmium sulfidezinc sulfide phosphor available from New JerseyZinc; Phosphor 511, zinc oxide, available from E. I. du Pont de Nemours& Co.; 1,1-diethyl-2,2-carbocyanine iodide; Permanent Violet Toner, CI.42535, Phosphotungstomolybdic acid lake of methyl violet available fromCollway Co.; and mixtures theerof.

The carrier liquid may comprise any suitable dielectric liquid. Thephotosensitive material may be dispersed in finely divided form in thecarrier liquid in any suitable concentration; typically about to percentby Weight may be used. Typical dielectric liquids include mineral oil,normal heptane, normal hexane, kerosene, petroleum ethers and mixturesthereof; also, parafiin, chlorinated hydrocarbons, and fiuorinatedhydrocarbons may be used where suitable.

Referring now to FIG. 1 there is illustrate an apparatus embodiment ofthe invention in its simplest form. As there shown, the apparatuscomprises a reservoir 1 containing and providing vertical head to aquantity of pigment containing electroviscous liquid ink 2 as describedabove. The lower portion of the reservoir is formed of two spaced apartelectrodes 3 and 4 defining an aperture 5 of about 8 to 12 mils and towhich a constant electric field is applied from a potential source 6.The lowermost portion of one of the electrodes extending along the slitaperture includes a transparent or translucent section 7 formedpreferably of electrically conduction material or having an electricallyconductive coating in contact with the ink. Commercialy available NESAglass comprising a transparent tin oxide coating or glass is suitablefor this purpose.

Aligned with the glass section 7 is a light source 8 which is energizedselectively from a signal source 9. Source 9 can represent a variety ofinputs as from a facsimile system, computer or the like and is operativeto control liquid flow by viscosity changes in the ink in response tothe applied radiation to which the ink is sensitive. Depending upon thechoice of liquid and pigment combination the ink viscosity will eitherincrease or decre in response to radiation such that in its lattercondition it flows through aperture 5 onto a recording web 11 advancingfrom a supply reel 15 to a take up reel 16. The signal from source 9should correspond to the liquid response to result in a right reading orreverse reading image on the web as desired. That is, if flow is arrestin response to radiation and a right reading image is desired, thesignal should ordinarily energize the light source during an absence oftransmitted information to be recorded and be deenergized wheninformation is to be recorded. This will result, for example, on coloredink depositing onto a white paper web to correspond with usuallyencountered positive type original documents.

The operative mechanism of the suspended pigment particles in theinsulating liquid is not fully understood, but is believed at least inpart to result from the responsive formation of loosely boundagglomerates of the photoconductive pigment particles in regions of highfield density and illumination at the aperture. Hydrostatic pressuresfor inducing flow are not critical and will of course vary with thematerials used and the flow rate required. That is, depending uponoperative conditions as will be understood, the ink should flow withsufficient density of deposit to form a legible indicia onto a recordingmember. At the same time flow should be arrested and resumed in responseto the applied and discontinuance of the light signal within a fractionof a second to ensure a good quality reproduction without blurring.

The voltage applied from potential source 6 in part controls the flow ofthe ink and may be either AC or DC. AC voltage is preferred in that theuse of a DC field tends to increase the danger of field breakdown givingpoorer control to the ink flow at the aperture. A suitable range of ACvoltage is from 600-1000 volts. Any minimum voltage shuld be sufficientto yield a controllable field satisfactory for the materials employed,while the maximum voltage is ordinarily that at which a field breakdownoccurs. ;When using AC voltage it has been found generally thatfrequencies exceeding 10 cycles/second causes a loss of flow control ofthe ink at the aperture.

Likewise the light intensity and wavelength at source 8 will be afunction of response sensitivities of the materials employed. With anink formed of a suspension of monastral green (5% by weight) in mineraloil and a potential of 600 volts AC applied between the electrodes, awatt incandescent projection bulb 8 when energized at a distance of 10inches arrested the ink flow. When the bulb was deenergized, the inkflow resumed resulting in a pattern on a recording web corresponding tothe on-ofi operational pattern of the light source. A similar result wasobtained with a suspension of Skyline Blue B-4712 (20% by weight) andmineral oil when subjected to a 1000-volt AC potential. With asuspension of Permanent Violet toner (11% by weight) in mineral oil ananalogous result was obtained with 600 volts AC applied and a SOD-wattprojection lamp at about a 12-inch distance.

Referring now to FIGS. 2 and 3, there is illustrated an array oflinearly aligned closely adjacent recording capillaries or pens 10 eachsimilar to that described above and terminating contiguously spaced tothe surface of a continuously advancing recording member 11 on which theink is to be selectively deposited. Extending beneath the recordingmember parallel and at least coextensive with the array of recordingpens is a platen 12 which supports the web member 11 as it passes belowthe pen array. A uniform hydrostatic pressure is applied from a source23 to an ink manifold 24 supplying ink to each of the individual pens.

The signal for controlling ink deposition from the individual recordingpens in accordance with this embodment emanates from a moving originaldocument 13 containing images 14 which are caused to move past ascanning slit 17 extending laterally thereacross and defined by spacedapart plates 18 and 19. As the document advances across the slit, theimages surface thereof is continuously illuminated by a plurality ofclosely adjacent fiber optic light pipes 20 receiving light fromtransversely extending lamp member 21 partially enclosed by shieldmember 22.

v The illuminated surface of the document is reflected into a pluralityof corresponding fiber optic light pipes 25 which extend from closeproximity to the document surface into an emission position relative tothe discharge end of each of the pens as described above. Accordingly,as the illuminated document advances, each incremental area thereof isscanned by a light pipe 25. With an ink composition responding to lightwith increased eleetroviscosity, the absence of sensing an image 14produces a light signal transmitted to the corresponding pen fiowcausing ink interruption to prevent deposition onto the recording member11. On the other hand, on sensing an image 14, there is a discontinuanceof light transmission through the respective optics such that the ink inthe corresponding pen will flow onto the recording member. As can beappreciated, each of the recording pens in the array are closelyjuxtaposed to each other as are their individual corresponding lightpipes 25 to provide optimum and maximum coverage of the document surfaceas well as the printout onto the recording member 11.

Because of direct signal transmission by which an absence of image ondocument 13 causes ink deposition from a corresponding recording pen 10onto recording member 11, there generally results a positivereproduction printout, i.e., image areas 14 will be represented by anink deposition on recording member 11 and vice versa. One method ofeffecting a reverse reproduction of the original is to employ a blacksurfaced recording member 11 with a white ink contained in thecapillaries.

An alternative and preferable method for rectifying the signal in orderto result in a positive-to-negative, or reverse reproduction isillustrated in FIG. 4. In accordance therewith, the emission end of thefiber optics 25 are connected to an intermediate electronic lightinverter 26, the output of which is connected via fiber optic lightpipes 27 to the recording pens as above. By this means a light inputsignal to the inverter will result in an absence of a light signal tothe corresponding pen, whereas an absence of signal into the inverterwill produce a light output signal thereto. This therefore results in afaithful positive-tonegative reproduction of the document surfacecontaining image areas 14 and permits the use of conventional whilepapers with colored inks in effecting this result.

Recording is effected in FIG. similarly as above and differs from theprevious embodiments in that the originating signal source can be otherthan optical. As here shown, the signal source 39 can be the output ofvarious electronic or sonar devices such as a computer, sound recording,or the like. The output of the source includes a plurality of individualleads 40 corresponding to the respective recording pens in the array andeach of the leads is connected to apply a signal to the transducer 41whereat the voltage signal from the source is converted to a lightoutput signal connected to light pipes 25. Thereafter, the apparatus isoperable as before.

In FIG. 6 the use of light pipes is omitted and the recording member 11advances continuously over a roller support 30. An electrical bias isconnected via potential source 6 to an array of recording pens 31 towhich ink is supplied from a manifold reservoir 24. An original copysheet 13 is caused to continuously advance past an exposure slit 33formed between transverse plates 34 and 35 and at which illuminationfrom lamp 36 illuminates the advancing portions of the copy surface.Instead of the fiber optic members employed as in the embodiment of FIG.2, the image 14 thereon in passing slit 33 is optically projected bymeans of objective lens 37 onto the array of recording pens 31 to effecta response similar to that described above. An apaque bar 38 extendstransversely across the surface of the moving recording member toprevent stray light from impinging on the recording pens as might becaused by unwanted reflection. By means hereof, the optical imageprojection of the incremental areas of the original passing overexposure slit 33 selectively affects each of the pens 31 in the array tocause ink deposition selectively in response to received illumination asbefore.

By the above description there isdisclosed novel method and apparatusfor a liquid ink recording system discriminately responsive to areceived optical signal for the selective deposition of ink onto arecording sheet. In accordance herewith, the ink composition ischaracterized by having photosensitive sensitivity such asphotoconductivity while in an applied electric field that becomeselectroviscously changeable upon exposure to actinic radiation to whichits photosensitive component is sensitive. By containing quantities ofthis ink under pressure in a plurality of closely spaced capillaryrecording pens, each of the pens subjected to a constantly appliedelectrical field can be rendered discriminately responsive to controlledink flow onto a recording member on receipt of an optical signalrepresentative of intelligence to be recorded. The apparatus can beadapted for either positiveto-positive or reversal reproduction and canbe operable with optical signals having optical origin or whateverorigin is known to those skilled in the art. While many light sensitivematerials have been specifically mentioned for use in the photoviscousinks, where desired, other viscosity varying materials may also be used.Typically, photochromic materials such as pyrospirans may be used.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specification shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:

1. A method of controlling the fiow of a photoelectroviscous recordingink for the recording of optical intelligence information comprising thesteps of:

(a) supplying under pressure a photoelectroviscous ink to an aperture inclosely spaced proximity to a recording surface so that saidphotoelectroviscous ink may flow through said aperture to said recordingsurface in the absence of actinic radiation.

(b) creating an electric field across said aperture and through saidphotoelectroviscous ink in the region proximate said aperture, and

(c) selectively arresting the flow of said photoelectroviscous inkthrough said aperture by exposing said ink most closely adjacent saidrecording surface to actinic radiation to which said ink isphotosensitive, said radiation being in the form of an optical signalrepresentative of intelligence to be transmitted.

2. A method of controlling the flow of a photoelectroviscous recordingink at an aperture for the recording of optical intelligence informationcomprising the steps of:

(a) supplying a photoelectroviscous ink to a discharge aperture definedby an opposed pair of electrodes, said aperture being in closely spacedproximity to a recording surface;

(b) applying sufficient pressure to said photoelectroviscous ink tocause it to flow through said discharge aperture;

(c) applying an electrical potential across said pair of opposedelectrodes defining said discharge aperture to create an electric fieldin said photoelectroviscous ink across said discharge aperture; and

(d) selectively exposing said photoelectroviscous ink in the region ofsaid discharge aperture to radiation to which said ink is photosensitiveto alter the fluid viscosity of said photoelectroviscous ink to modulatesaid photoelectroviscous ink flow therefrom onto said recording surfacein response to radiation received directly from an optical signalrepresentative of the intelligence to be transmitted.

3. A facsimile recording apparatus comprising in combination:

(a) a container containing a pressurized quantity of photoelectroviscousink having photoconductive properties and including opposed electrodesdefining an ink discharge aperture in said container, said electrodesterminating on the same side of and adjacent the surface of a recordingmember on which a recording is to be made;

(b) electrical potential means connected to apply an electric fieldbetween said opposed electrodes at said ink discharge aperture; and p(c) means for transmitting radiation intelligence to the ink to saiddischarge aperture whereby the fluid viscosity of thephotoelectroviscous ink is altered to control the fiow of saidphotoelectroviscous ink from said discharge aperture so that the periodof flow interruption correspounds to the duration of the applied opticalradiation.

4. Apparatus according to claim 3 in which there is included an array ofsaid containers and means to effect relative movement between therecording member and said container array.

5. Apparatus according to claim 4 in which said means for transmittingradiation intelligence to the ink at said discharge aperture to effect acontrolled ink flow from said container onto said recording membercorrelated to the radiation transmitted includes means to project acontinuous image pattern of light and shadow from an ori ginal documentacross said array of said containers.

6. Apparatus according to claim 4 in which said transmitting meansincludes a plurality of light fibers each aligned to separately transmitradiation to a different container of said array.

7. Apparatus according to claim 4 in which there is included a signalsource to emit voltage signals of intelligence to be recorded and meansto transduce said voltage signals to radiation signals to be transmittedby said transmitting means.

8. Apparatus according to claim 4 in which there is included means toscan the image surface of an image bearing document to form theintelligence input to said transmitting means.

9. Apparatus according to claim 8 inwhich there is includedlight-inverter means intermediate said scan means and said transmittingmeans to invert the radiation signal input to said transmitting means. Ii

10. A recording apparatus comprising in combination: (a) electrode meanscomprising at least two electrodes defining an aperture in part, saidelectrodes residing on the same side of and adjacent the surface onwhich a recording is to be'made; v (b) electrical potential meansconnected'to apply an electric field between said electrodes; 7 (c)photoelectroviscous inking means including a photoelectr'oviscous inkhaving photoconductive properties, said photoelectroviscous ink beingwithin the electric field of said electrodes in at least, the region ofsaid electrodes most closely adjacent to said surface on which therecording is to be made and means to exert pressure on saidphotoelectroviscous inkj and ((1) optical control means for transmittingradiation intelligence to said photoelectroviscous ink in the region ofsaid electrodes most closely adjacent to said surface on which therecording is to be made whereby the fluid viscosity of thephotoelectroviscous ink is altered to control the flow of saidphotoelectroviscous ink from said electrode means to the recordingsurface so that the period of flow interruption corresponds to theduration of the applied optical radiation.

References Cited UNITED STATES PATENTS 3,270,637 9/1966 Clark 13,308,475 3/1967 Bean 346 3,480,962 11/1969 Weigl et a1 346-1 JOSEPH W.HARTARY, Primary Examiner US. Cl. X.R. 34.6140

